This invention relates to control apparatus for a vehicle mounted power antenna, and particularly to that portion of the control which causes the drive motor to cease its operation at the proper time while limiting stress on the drive mechanism.
The typical commercial power antenna apparatus has drive means for extending or retracting the antenna relative to the vehicle body which is controlled in response to a signal from the vehicle radio. When the radio is turned on, a signal is sent to the antenna control to initiate extension; and extension continues until full extension is attained, usually as indicated by a reaction switch. When the radio is turned off, a signal is sent to the antenna drive to initiate retraction; and retraction continues until full retraction is attained, as indicated by the reaction switch. The reaction switch responds to the high force in the antenna drive mechanism which is produced when the antenna stalls at the limit of its operation, either fully extended or fully retracted. However, the high stress of a hard stall at full stall current, repeated with every antenna actuation, increases wear and fatigue of the drive cable and is thus undesirable. The useful life of the antenna drive cable and perhaps the remainder of the antenna drive mechanism might be extended if the control were able to stop the antenna in the desired position while limiting the stress on the antenna drive mechanism.